The American Lung Association released State of the Air 2013, an annual report on air quality April 24, 2013 which lists both the cleanest and most polluted areas in the country. This year's report shows significant progress in efforts to reduce ozone and particulate pollution in the Greater Bay Area (San Francisco-Oakland-San Jose). Air pollution continues to threaten the health of Bay Area residents, but the overall trend is toward cleaner air. The findings reinforce the effectiveness of local and state clean air laws and progressive initiatives including incentive programs that help reduce diesel emissions and promote cleaner vehicles and fuels.

"The State of the Air 2013 report shows that California is continuing the long-term trend to cleaner and much healthier air," said Jane Warner, President and CEO of the American Lung Association in California. "However, our report also shows that air pollution continues to put lives at risk throughout the state. We must step up our efforts to cut pollution so all Californians can breathe clean, healthy air."

The Greater Bay Area shows noteworthy success in reducing both ozone and particulate pollution over the years of the State of the Air report. The region experienced a 65 percent decline in unhealthy ozone days since the State of the Air began collecting data in 2000, and there also have been dramatic reductions in both short term and annual levels of particle pollution. The region has come into attainment of the annual particle pollution standard, with all counties earning a "PASS" while the average number for unhealthy short-term particle pollution dropped more than 80 percent since the 2004 report.

Overall, California cities still dominate lists for the most polluted areas in the nation for ozone (smog) as well as short-term and annual particle pollution. Specifically, of the top ten cities with the worst air pollution, California municipalities rank as follows:

California's slow yet steady progress toward healthy air can be attributed to its strong history of leadership on air and climate policies. The Bay Area Air Quality Management District's wood-burning regulation also has been instrumental in improving air quality in the region. Wood smoke is the single, largest source of particulate matter emissions in the Bay Area.

California's pollution problems are primarily caused by emissions from transportation sources including cars, diesel trucks and buses, locomotives, ships, as well as agricultural and construction equipment. Air pollution problems also are caused by emissions from oil refineries, manufacturing plants, and residential wood burning. In addition, California's warm climate promotes the formation of ozone pollution, and valleys and mountains in the central and eastern portions of the state trap pollution where it can linger for days and put residents at risk for the onset or exacerbation of lung disease.

Note: Alameda County received an F for ozone (smog) pollution and a D for short term particle pollution (soot).

For more information on the American Lung Association State of the Air Report and a list of steps individuals can take to clean the air, the public should visit www.lung.org/california or call 1-800-LUNG-USA (1-800-586-4872).